[P-EM12] 大気圏ー電離圏結合

[PEM12-P06] Analysis of VLF Band Waves near the Sq Current System observed by S-310-44 Sounding Rocket

*三宅 壮聡¹、中村 龍一郎¹、石坂 圭吾¹、阿部 琢美²、熊本 篤志³、田中 真⁴ (1.富山県立大学工学部電子・情報工学科、2.宇宙航空研究開発機構 宇宙科学研究所 太陽系科学研究系、3.東北大学大学院理学研究科地球物理学専攻、4.東海大学　情報教育センター)

キーワード：電場、Sq電流系、ロケット観測、電離圏

The Sq current system is one of the ring current which occurs in the lower ionosphere in the winter daytime. It is caused the specific plasma phenomena such as electron heating and strong electron density disturbance. S-310-44 sounding rocket experiment was carried out to investigate the special phenomena near the Sq current focus, at 12:00 JST on January 15th, 2016. The rocket passed through the Sq current focus, and all the scientific instruments onboard the rocket worked successfully. In this experiment, the Electric Field Detector (EFD) observed the VLF band AC electric fields up to 6.4kHz in the altitude from 100km to 160km. We made the altitude profile of the electric field spectra, and found clear VLF band waves with the frequencies from 2kHz to 3kHz at the altitude about 100km. These VLF band waves are observed during only the rocket ascent. The Fast Langmuir Probe (FLP) observed that the electron temperature increase about 150K larger than the background in this region, and the frequency variation of the VLF band waves shows good correlation with the electron temperature as shown in Figure 1. According to the polarization analyses, the electric fields of the VLF band waves are oblique, not parallel to the magnetic field. The frequency range of this VLF band waves is consistent with the ion cyclotron frequency. These results suggest that the VLF band waves observed in this experiment are one of the ion cyclotron harmonic waves whose frequencies vary with the temperature ratio of the electron and the ion (Te/Ti ). We are going to investigate further the VLF waves observed by the rocket experiment, and clarify the heating mechanism of the electrons near the Sq current focus.